Intensity over time

[Portisblaed]

Hi everyone,

I have the following problem...
I am trying to plot some Light Intesity values over time out of a real time video. But I don't know how to create my VI ...
Therefore I have attached the VI I have until now. It first asks for a region of Interest by pushing the Setup-Button and after that the Measurement of the Intensity begins, shown in the second tab called "real time video"... the values are also shown in the box beside!

Now I don't know how to measure the time und how to write the time and intensity values in an array to plot it...
It would be best to capture the time value for every frame and consequently every intensity value...
Any ideas ???

I am using LV 8.0 ...I don't have a higher version


Message Edited by Portisblaed on 12-29-2007 07:03 AM

[Sarah_Coleman_NIUK]

Hi there,

Do you want the time information for any other reason then for plotting the data? ie, for post-analysis?

If not, you can just plot the mean intensity directly on a chart and change the format and precision of the chart to display time information on the x-axis.

[Portisblaed]

Hi,

thank you very much, that's a good start. BUt I think I need the time, because I am measuring a signal, then I am plotting it and last I want to get out the oscillation frequency by a Fourier Transform ! I think I need the time values for the FFT. Do you know how to go on?

[rsw]

Hi,

If you take a look in the example finder LabVIEW > Help > Find Examples and search for "fourier" there are a number of fourier transform examples, some of which transform into the time domain, this may help you with what your needing to do. If not please let me know and I'll look into it further for you.

Regards,

[Portisblaed]

Hi,

I have one more question about the waveform chart...
When I play an AVI file with about 50 seconds time, and I plot the Intensity over time with the waveform chart, this plots shows me a timescale which doesn't fit to the time fro m the video! For example my 50 second video is played in a time of 20 seconds! What's the reason for that? Do I have to change the time settings somehow?

And the examples don't really help me to fourier transform the signal I got, because I don't know the time of the measurement! Just the x-scale of the wavefrom chart like you suggested it before...

Thanks for help!


Message Edited by Portisblaed on 01-08-2008 09:50 AM

[rsw]

Hi,

The AVI file your playing does it have any specific encoding i.e. DivX/XVid? I will try to reproduce this issue today and get back to you with an answer on that,

Thanks and apologies for the late reply,

All the best,